Houston (CNN) -- Homicide detectives here say they are exploring every possible avenue, as they investigate the assassination-style killing of an Iranian dissident in mid-January.
Gelareh Bagherzadeh, 30, was shot and killed on January 15 as she drove her father's car home just before midnight. She was studying molecular genetic technology at the University of Texas MD Anderson Cancer Center in Houston.
"The evidence indicated that she had been shot through the passenger side window," Houston Police Sgt. J.C. Padilla said. "She was shot one time, and an autopsy revealed she had been shot in the head."
Bagherzadeh had come to Houston in 2007, her friends said. Before her arrival, they say, she had traveled throughout Europe, living in Paris and, for a time, in Budapest.
Her father had once worked for the Iranian Oil ministry, according to police.
In 2010, not long after the disputed presidential elections in Iran, Bagherzadeh joined a group called SabzHouston, formed to protest the election results. She was videotaped by a reporter for the Houston Chronicle while on a street corner, saying she was showing support for "brothers and sisters suffering in Iran."
"That's why we gather here," she said in the taped account, "to be their voice here and show them we are together, and they are not alone."
She wasn't scared to show her face, but she said she wouldn't give her last name to reporters for fear of retaliation.
Police investigating her killing have found no one who would have wanted to kill Bagherzadeh. With nothing stolen or missing, they've ruled out a random robbery. Police said they are looking into whether her involvement with the protest movement had anything to do with her killing.
"Right now ... because of obvious reasons, we're exploring those issues that she was advocating," Padilla said.
Houston police on Monday announced they have doubled the reward from $5,000 to $10,000 for any information leading to the arrest and conviction of the person responsible for Bagherzadeh's death.
The night she was killed, she was driving to the condominium she shared with her parents not far from downtown Houston, according to police. It was about 11:45 p.m. and, investigators said, she was on her cell phone with an ex-boyfriend.
Police said the boyfriend heard a scream followed by tires screeching and then silence. She was found slumped over the steering wheel, the tires of the car still spinning because it had crashed into a garage in a nearby condominium complex. The ex-boyfriend, according to police, is not considered a suspect.
Members of the Sabz dissident group wondered why Iran might target Bagherzadeh, particularly because "there are many more important opposition leaders" in the United States, according to group member Seth Eslami.
"There are groups who have their own TV stations, groups who lobby in Washington, D.C., groups who actually plot in Iran to do different things. Not us," Eslami said. "Why us?"
Two years ago, CNN reported on what local police in Glendora, California, said was Iranian involvement in the attempted assassination of an Iranian dissident radio broadcaster. Since then, the United States has formally accused Iran of being behind a plot to kill the Saudi Arabian ambassador to the United States.
Fred Burton, a senior vice president of a private security analytical firm, Stratfor Global Intelligence, said Iranian intelligence services work in secretive ways, with motives that aren't always clear.
Burton, a former State Department expert on counterterrorism, said the fact that the victim lived in Paris and traveled widely in Europe could have made her far more important to Iranian intelligence than her dissident activities in the United States.
"You have a 30-year-old woman who's spent time out of Iran, in Paris for example," he said, "What has she been doing? Was she more active overseas, for example, than we understand here? The Iranian intelligence service has a very strong network, a very strong collection network in Paris specifically. They are trying to keep tabs on their dissidents."
Houston police said they are stuck and will follow any lead, even those involving Iranian conspiracies, if it will lead them to the killer.
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